Integrated hydroponic and wetland wastewater treatment systems and associated methods

ABSTRACT

The wastewater treatment systems have a plurality of treatment modules between the inlet and the outlet, each for treating water with a selected process. Influent is directed to a covered anaerobic reactor, and then to an attached growth pretreatment filter that is at least intermittently exposed to atmospheric oxygen. Following the filter is a hydroponic reactor followed by a vertical-flow wetland. A second embodiment includes, following the filter, a tidal vertical-flow wetland and a pump for recycling water exiting the wetland upstream of the filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/294,456.“Integrated Hydroponic and Fixed-Film Wastewater Treatment Systems andAssociated Methods,” filed Nov. 14, 2002, now U.S. Pat. No. 6,830,688,which itself claimed priority to provisional application 60/333,203,filed on Nov. 14, 2001, entitled “Integrated Hydroponic and Fixed-FilmWastewater Treatment Systems and Associated Methods”, and 60/389,637,filed on Jun. 18, 2002, entitled “Residential Wastewater TreatmentSystem and Associated Method”. The disclosures of these applications areincorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wastewater treatment systems andmethods, and, more particularly, to such systems and methods forwastewater treatment that are nonchemically based.

2. Description of Related Art

Wastewater treatment via “natural” means, i.e., without the addition ofchemicals, has been accomplished with the use of aquatic and emergentmacrophytes (plants) that, in concert with the attendant microorganismsand macroorganisms associated with macrophyte roots and stems,substantially mineralize biodegrade organic materials and substantiallyremove certain excess nutrients, such as nitrogen and, to a lesserextent, phosphorus. These macrophytes have typically been located inartificial marshlands, also known as constructed wetlands, which aredesigned for gravity flow. A negative aspect of such systems is thatthey are very land-intensive, requiring roughly on the order of 100times as much land area as a conventional treatment plant, or, in termsof capacity, as much as 30-40 acres per 10⁶ gallons of wastewatertreated per day unless other treatment processes are incorporated intothe constructed wetlands.

Subsurface-flow wetlands, which comprise aquatic plants positioned abovea gravel filter, are also known for use in wastewater treatment. Thesesystems have been shown to frequently fail, however. Failure ismanifested as the upstream gravel tends to become clogged withbiosolids, permitting the influent to bypass the clogged region and passsubstantially untreated to a downstream region. Additionally, surfacewastewater is a breeding ground for disease vectors and nuisanceinsects. Ultimately the gravel becomes so clogged that design wastewatertreatment is substantially compromised. Plants also appear to havelittle treatment role in subsurface flow wetlands because the plant rootsystems are inhibited by conditions in the gravel filter from growingsufficiently long to extend into the gravel, and thus have minimalcontact with the influent.

Several varieties of aquatic and emergent macrophytes are known to beused in wetland and aquatic wastewater treatment systems, including, butnot limited to, cattails, bulrushes, sedges, and water hyacinths. Inwetland treatment systems these plants may be packed in unlined or linedtrenches or basins filled with a granular porous medium such as gravelor crushed stone. It has also been suggested to use recycled, shreddedscrap tires in the place of the gravel. Another suggested wetland systemvariant is to place a semipermeable barrier between a lower level intowhich effluent enters and the plant root system for directing thewastewater flow across the entire plant bed.

In yet another variant, floating aquatic macrophytes, typically waterhyacinths, are placed in shallow lagoons where plant roots, withattendant microorganisms and macroorganisms, extending into the watercolumn are a principal design treatment mechanism. Although this rootzone treatment method can provide advanced secondary treatment effluent,its application is limited by climate and available sunlight toapproximately 5% of the United States. The large treatment footprint ofwater hyacinth treatment systems prohibits enclosure in greenhouses foralmost all economically viable applications.

It is also known to combine plant root zone treatment with conventionalactivated sludge technology. The principal advantages of combining rootzone treatment with activated sludge are improved nutrient removalcapability over root zone treatment alone and improved treatmentstability in small, activated sludge treatment systems. Among theproblems encountered with root zone/activated sludge technology is thatthe clarifiers employed do not scale well when the size of the system isreduced beyond a certain point. In addition, operator qualifications arehigh for activated sludge systems, adding to the expense of running thesystem. Root zone/activated sludge technology has been known to digestin situ a large fraction of the biosolids produced and maintained withinthe treatment system, thereby reducing system biosolids yield. Themechanism for yield reduction is thought to be the retention ofbiosolids flocs on plant roots with subsequent consumption andmineralization of flocs by the invertebrate community attendant to theroot zone. Reduction of yield is desirable only to a certain point,however. As reactors in series are added, thereby increasing biosolidscontact with the root zone, yield may be reduced to the point where aninsufficient quantity of biosolids remains to be recycled from theclarifier to the reactors in series. Lack of recycled biosolidssubstantially degrades the treatment performance of the activated sludgetreatment element. This design trap is inherent to root zone/activatedsludge treatment systems.

Preliminary studies have been performed on various aspects of thepresent invention by the inventors and other colleagues, and these havebeen reported in “Final Report on the South Burlington, Vt. AdvancedEcologically Engineered System (AEES) for Wastewater Treatment,” D.Austin et al., 2000; and “Parallel Performance Comparison betweenAquatic Root Zone and Textile Medium Integrated Fixed Film ActivatedSludge (IFFAS) Wastewater Treatment Systems,” D. Austin, WaterEnvironment Federation, 2001; both of these documents are incorporatedherein by reference in their entirety.

SUMMARY OF THE INVENTION

The present invention provides a wastewater treatment system and methodthat are less land intensive than previous systems, as well as combiningthe advantages of a plurality of remediation techniques. The presentinvention has a smaller footprint than previously disclosed wetlands,reduces undesirable characteristics of an influent, and has a low yield,i.e., low proportion of matter needing disposal.

An additional feature of the invention provides a unified environmentthat includes a remediation system, as well as a method of doingbusiness incorporating the water treatment systems of the presentinvention.

The wastewater treatment systems and methods of the present inventionare amenable to the treatment of, for example, but not intended to belimited to, domestic wastewater, industrial waste or process water,urban runoff, agricultural wastewater or runoff, and even biologicalsludges. The systems are capable of handling a flow range ofapproximately 2000-2,000,000 gal/day. The types of contaminants that canbe treated in the system include suspended particles, nutrients, metals,simple organics (oxygen-demanding substances), and synthetic or complexorganics. The undesirable characteristics typically desired to beremediated include, but are not intended to be limited to, averagebiological oxygen demand (BOD), average total suspended solids (TSS),total nitrogen, and concentration of oil and grease. The systems of thepresent invention can reduce BOD to <10 mg/L, TSS to <10 mg/L, and totalnitrogen to <10 mg/L.

The water treatment system of the present invention comprises awastewater inlet, a treated water outlet, and a plurality of treatmentmodules between the inlet and the outlet. Each module is for treatingthe water with a selected process. Each module is in fluid communicationwith at least one other module for permitting sequential treatment ofthe wastewater by a plurality of processes.

Influent wastewater is first directed to a covered anaerobic reactor,which serves to perform an initial organic and solids removal. In thisvessel the solids from the influent settle, and anaerobic bacteria feedon the solids and wastes in the liquid. A filter is provided forremoving odors from gases that are produced herein.

A first embodiment of the present invention includes a system foradvanced treatment of wastewater. This system comprises an attachedgrowth pretreatment filter that is at least intermittently exposed toatmospheric oxygen. The filter has an inlet for receiving water to betreated.

Following the filter are a first and a second hydroponic reactor, eachhaving an inlet and an outlet. Hydroponic reactors are aerated reactorsthat have a rigid rack set at the water surface to support plants thatsend down roots into the wastewater column. The rack preferably coverssubstantially the entire water surface. Plants preferably substantiallycover the entire surface of the rack.

A vertical-flow wetland comprises a basin having an outlet in a bottomthereof, and comprises a plurality of treatment regions through whichthe water to be treated passes under gravity flow. The basin is adaptedto contain a particulate medium, and a mat positioned above theparticulate medium is adapted for permitting plants to root therein. Thewetland cell is adapted to maintain a population of aquaticinvertebrates therein. Water entering the top of the vertical-flowwetland thus passes through a treatment zone formed by the plant roots.Beneath the root zone lies the particulate medium, such as, for example,an expanded shale aggregate for phosphorus absorption, solidsfiltration, nitrification, and BOD removal.

Water is transferred from the filter outlet to the first reactor inlet,and from the first reactor outlet to the second reactor inlet, andfurther is distributed from the second reactor outlet across at least aportion of the vertical-flow wetland.

If desired or necessary, water emerging from the vertical-flow wetlandmay be recycled either to the anaerobic reactor or to the filter foradditional treatment. The final effluent may be subjected to additionaltreatment such as ultraviolet disinfection. The water emerging from thesystem is then suitable for reuse.

A second embodiment of the system is also directed to a system foradvanced treatment of wastewater. This system also comprises an attachedgrowth pretreatment filter that is at least intermittently exposed toatmospheric oxygen. The filter has an inlet for receiving water to betreated.

The system further comprises a first and a second tidal vertical-flowwetland (TVFW). The TVFW can be constructed in a plurality ofconfigurations, and can include a first lagoon that has an inlet forreceiving wastewater to be treated and a first vertical flow wetlandcell that has an outlet adjacent a bottom thereof. A first means fortransporting water from the first lagoon to the first wetland cell isprovided.

The TVFW can also include a second lagoon that has an inlet forreceiving water from the first wetland cell outlet and a second verticalflow wetland cell that has an outlet adjacent a bottom thereof. A secondmeans for transporting water from the second lagoon to the secondwetland cell is provided.

Means for recycling at least a portion of the water exiting the secondwetland cell outlet to the first lagoon can also be provided.

Throughout the subsequent discussion, the definitions of lagoon andwetland cell will be generally taken as follows: The first and thesecond lagoon are adapted to function essentially aerobically and tocontain plants having roots positioned to contact water flowingthereinto. The first and the second wetland cell are adapted to containplants having roots positioned to contact water flowing thereinto.

The integrated TVFW treatment system of the present invention in aparticular embodiment includes alternating wetland cells and lagoons.The overall hydraulic regime in this system involves fill and draincycles wherein wastewater is alternately pumped between cells andlagoons. The vertical flux of water in and out of the wetland cells isdesigned to cycle over a predetermined period, and is therefore referredto as tidal.

It is to be understood that reference to first and second wetland cellsor lagoons in no way limits the total number of wetland cells or lagoonsin series. In embodiments where several wetland cells and lagoons areemployed the flow regime is a logical serial extension of the flowdescribed herein between the fist and second lagoon/wetland cell pair.For example, recycle flow from the second lagoon wetland cell pair isunderstood to represent recycle from the final lagoon/wetland cell pair.

Hydraulic design integrates passive forward flow, tidal flow, andrecycle flow into one system. The process design in various embodimentsintegrates wetland and lagoon treatment technology. The process designof the present invention also includes elements of environmental andecological engineering design that significantly improve the state ofthe art of wastewater treatment in general, and wetland wastewatertreatment in particular.

In the TVFW, wastewater to be treated is subjected to a firstsubstantially aerobic environment containing aquatic invertebrates for afirst time period and is transported from the first aerobic environmentto a surface of a first substantially anaerobic/anoxic environmentcontaining plants having roots for a second time period. Aquaticinvertebrates consume a substantial fraction of biomass produced withinthe system.

Water emerging from beneath the plant roots of the firstanaerobic/anoxic environment is next transported to a secondsubstantially aerobic environment containing aquatic invertebrates for athird time period. Water from the second aerobic environment is thentransported to a surface of a second substantially anaerobic/anoxicenvironment containing plants having roots for a fourth time period.Aquatic invertebrates consume a substantial fraction of biomass producedwithin the system.

At least a portion of the water emerging from beneath the plant roots ofthe second anaerobic/anoxic environment is then recycled to the firstaerobic environment.

Water is distributed from the filter outlet across at least a portion ofa surface of the first wetland and also from a bottom of the firstwetland across at least a portion of a surface of the second wetland.Water is also recycled from a bottom of the second wetland to a locationdownstream of the filter.

If desired or necessary, water emerging from the second TVFW may berecycled either to the anaerobic reactor or to the filter for additionaltreatment. The final effluent may be subjected to additional treatmentsuch as ultraviolet disinfection. The water emerging from the system isthen suitable for many reuse applications requiring wastewater treatedto advanced standards. The features that characterize the invention,both as to organization and method of operation, together with furtherobjects and advantages thereof, will be better understood from thefollowing description used in conjunction with the accompanying drawing.It is to be expressly understood that the drawing is for the purpose ofillustration and description and is not intended as a definition of thelimits of the invention. These and other objects attained, andadvantages offered, by the present invention will become more fullyapparent as the description that now follows is read in conjunction withthe accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the first embodiment of the presentinvention.

FIG. 2 is a cross-sectional view of an exemplary hydroponic reactor(lagoon) of the present invention.

FIG. 3 is a side cross-sectional view of a vertical-flow wetland moduleof the embodiment of FIG. 1.

FIG. 4 is a schematic diagram of the second embodiment of the presentinvention.

FIG. 5 is a schematic diagram of an exemplary time sequence of waterflow between portions of the system of the present invention.

FIG. 6 is a schematic illustration of a unified environment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description of the preferred embodiments of the present invention willnow be presented with reference to FIGS. 1-6.

A schematic of a first embodiment of the present invention (FIG. 1)illustrates the flows through this system 10, beginning with wastewaterinfluent 90 entering via an inlet 11 into a covered anaerobic reactor12, which serves to perform an initial organic and solids removal. Inthis vessel 12 the solids from the influent 90 settle, and anaerobicbacteria feed on the solids and wastes in the liquid.

Following treatment in the anaerobic reactor 12 for a predeterminedperiod, for example, in a particular embodiment 1.5 days comprises anexemplary retention time, the wastewater 90 is channeled via a pump 13to the inlet 14 of an attached growth pretreatment filter 15. Thisfilter 15 is at least intermittently exposed to atmospheric oxygen. Thefilter 15 achieves removal of organics and solids and denitrification.

Fluid is collected from the bottom 16 of the filter 15 and is pumped 17to an inlet 181 of a first hydroponic reactor 18 (FIG. 2). Herein theterm hydroponic reactor is taken to comprise an aerated reactor vessel23 that has a substantially rigid rack 19 set at the surface of water 90in the reactor 18. The rack 19 supports plants 21 that send down roots22 into the wastewater column 20. Preferably the rack 19 coverssubstantially the entire water surface. Also preferably the plants 21cover substantially the entire surface of the rack 19.

Water from the first hydroponic reactor 18 is pumped 21 or flows bygravity from an outlet 182 to a second hydroponic reactor 18′ that issubstantially identical to the first 18.

Water from the second hydroponic reactor 18′ is then pumped or flows bygravity to the top of a vertical-flow wetland 24 (FIG. 3), where adistribution manifold 25 doses the surface of the wetland 24 fordownward, gravity-driven flow through a plurality of zones. The wetland24 continues BOD removal, nitrifies and denitrifies, and removes TSS.The manifold 25 is pressurized sufficiently to ensure adequatedistribution across manifold orifices or outlets, and the spacing oforifices or outlets 26 therein is on a spacing of, for example, 1-ftcenters. The use of vertical-flow wetland technology can reduce thefootprint of the process by 50-75%.

The wetland 24 comprises a top dressing 27 that may comprise, in certainembodiments, a layer of soil, for example, 6 in. The soil 27 comprisesin a preferred embodiment a slightly limiting soil, with a percolationof 2 in./min, with no particle size >2 mm, that is, coarse sand. Thepurpose of the top dressing 27 is to prevent public exposure to thewastewater in the wetland 24, to control odors, and to improveappearance. The top dressing 27 is placed in covering relation to thedistribution manifold 25.

Beneath the distribution manifold 25 is positioned a layer of wetlandsod 28, which in a preferred embodiment comprises a cocoanut fibermatting known as “Coir” that is embeddable with wetland plants 29. Thewetland plants 29 provide an extensive root 30 mat, which preferablycover approximately 70% of the mat 28 bottom, and comprises an aquaticroot zone. The sod 28 preferably covers substantially the entire surfaceof the wetland 24. The distribution manifold 25 atop the sod 28 causesinfluent flow to pass through the root mat 30 of the plants, whichdiversifies the microbial community and removes BOD and TSS. The rootmat 30 and the sod 28 act as a prefilter to the lower-lying zones. Theroot mat 30 at the level of the wetland sod 28 is preferably not floodedfor extended periods in order to maintain aerobic conditions.

The species of plants 29 have been empirically verified as being hardyunder conditions of wastewater loading of the particular site in whichthey are being employed. The wetland sod 28 permits effectiveinstallation of healthy plants 29 to enable the creation of asubstantially “instant” wetland litter layer 24 that is habitat for manyinvertebrate species associated with wetland ecosystems in nature.

The next zone beneath the wetland sod 28 comprises a layer ofmanufactured medium 31 comprising, for example, random-packed plasticmedium such as high-density polyethylene or polyethylene, having a depthof approximately 1.0-3.0 feet. The purpose of this medium 31 is BODremoval, TSS removal, and nitrification over the provided high surfacearea of the medium. The plastic medium 31 permits easy penetration ofplant roots and a reliably moist and aerobic environment fordetritivores to thrive on biofilms growing from wastewater nutrients. Ina preferred embodiment, not intended to be limiting, the mediumcomprises textured cylindrical pieces approximately 4-10 mm in diameter,and having a height smaller than the diameter. The medium's 31 porosityis approximately 90%. The thin-film chemistry on the medium enhances BODremoval and nitrification, and the bulk liquid chemistry in the floodedstate enhances denitrification by the rapid formation of anoxicconditions. The frequent (e.g., several times per day) exposure ofbiofilms formed on the medium assists in the decomposition of thebiofilms into trace organics, carbon dioxide, and water.

Effluent trickles through the media/root mixture in thin films and thenenters a layer of lightweight aggregate 311 of particle diametersubstantially not less than one millimeter. The aggregate comprises amanufactured aggregate of consistent quality that can be penetrated byplant roots. Remaining suspended solids are filtered out in theaggregate layer. Nitrification also takes place in the aggregate layer311.

The next lower-lying zone comprises a rock or gravel aggregate layer 32,preferably expanded shale aggregate, most preferably with a particlediameter not substantially less than four millimeters. The purpose ofthis layer 32 is phosphorus absorption, TSS filtration, nitrification,and BOD removal. The bulk liquid chemistry in the flooded state enhancesdenitrification by rapid formation of anoxic conditions. In a preferredembodiment the depth of this layer 32 is approximately 1.5-2.0 feet.Preferably this layer 32 is intermittently flooded, during which timethe gravel layer 32 becomes anoxic. A portion of waste nitrified in thelayers above are denitrified in the flooded section. As the liquid levelof the flooded gravel layer 32 rises, a drainage device is triggered,draining the entire gravel layer 32 through a bottom drain system.Draining the gravel layer 32 pulls air into the gravel interstices, andexposure of biofilms to air prevents buildup of biofilms that could clogthe gravel layer 32.

Beneath the rock/gravel aggregate layer 32 is positioned an under-drain33 having a plurality of holes 34 for collecting fluid draining throughthe rock aggregate layer 32. The under-drain 33 effluent flows to aneffluent pump vault 35, which controls the elevation of the wetland 24and contains a pump 36 that lifts effluent 90′ to a series of valves37-39, each with flow meters 40-42 attached thereto, leading to tworecycling paths 43,44 and to a discharge 45. The effluent 90′ to berecycled is channeled either to the anaerobic reactor 12 (path 44) or tothe fixed-film reactor 15 (path 43) for additional treatment. The finaleffluent 90′ is typically spit between the recycling path 45 and adischarge 45 at a predetermined ratio, such as 3:1, although this is notintended as a limitation.

The rate of recycling preferably recycles an average drop of water fromthe primary tank 12 1-5 times, which permits a high level of treatmentin the wetland 24.

The discharge 45 may lead to an additional treatment device such as anultraviolet disinfection module 46. The water emerging from the system10 is then suitable for reuse, and a second sample port 47 is providedfor additional testing.

Discharge 45 can include discharge by gravity directly to a leach fieldor soil absorption system, discharge to a subsurface irrigation system,and, where allowed by local regulations, discharge to surfaceirrigation. Subsurface irrigation may include, for example, a pump and aplurality of small, flexible pipes with emitter openings. The irrigationdistribution network preferably lies close to the surface in warmclimates in the biologically active root zone area of soil.

In a second embodiment of the invention, the system 50 (FIG. 4)comprises a pretreatment module 51, into which influent 90 is channeledand permitted to reside for a predetermined period. The wastewater 90 isthen channeled to via a pump 52 to the inlet 14 of an attached growthpretreatment filter 15 as above. This filter 15 is at leastintermittently exposed to atmospheric oxygen. The filter 15 achievesremoval of organics and solids and denitrification.

Water from the filter 15 is transferred to a pair 53,54 of tidalvertical-flow wetlands (TVFW), each of which comprises alternatingseries of lagoons 55 and VF wetland cells 56. Each lagoon 55 (FIG. 2) iscomparable to the hydroponic reactor 18 discussed above. Each lagoon 55is adapted to maintain a population of grazing aquatic invertebrates,such as, for example, filter-feeding zooplankton.

Each wetland cell 56 comprises a module 24 as illustrated in FIG. 3. Thewetland cell 56 has a depth 67 that is less than that 58 of the lagoon55. However, the surface area of the lagoon 55 is preferablysubstantially smaller than that of the wetland cell 56. The wetland cell56 is adapted to maintain a population of aquatic invertebrates, suchas, but not intended to be limited to, detritivores.

Each TVFW 53,54 may comprise a plurality of wetland cells 56 a-56 c andlagoons 55 a-55 d, alternating as shown in FIG. 5. Q represents forwardflow; Q_(r), recycle flow. The overflow piping between wetland cells 56a-56 c and lagoons 55 a-55 d is not depicted. The dashed horizontal linein the wetland cells 56 a-56 c represents the media/plant root surface.The overall hydraulic regime in the TVFW 53,54 involves fill and draincycles where wastewater is alternately pumped and flows between cells 56and lagoons 55. The vertical flux of water in and out of the wetlandcells 56 a-56 c is designed to cycle over a predetermined period of, forexample, at least once per day, and is therefore referred to as tidal.

Means for transporting water between the lagoons 55 a-55 c and wetlandcells 56 a-56 c alternately are provided, as well as recycling betweenthe fourth lagoon 55 d and the first lagoon 55 a. These may comprise,for example, pump stations 73 a-73 d associated with each lagoon 55 a-55d (FIG. 5). Generally water flows from the wetland cells 56 a-56 c intotheir respective lagoons 55 b-55 d passively, as will be discussed inthe following. In some embodiments, a pump station alone may be usedwithout an associated lagoon 55.

In the embodiment shown in FIG. 5, for example, the pump 73 a in thelagoon 55 has an intake positioned lower in the lagoon basin than thelagoon inlet. A level sensor may be employed in certain embodiments foractivating the pump when a level of water in the lagoon 55 reaches apredetermined depth, for example, to prevent flooding.

In a particular embodiment (FIG. 5), the recycling pump 74 d is adaptedto recycle a water portion in a range of 50-500% of the wastewatervolume entering the first lagoon 55 a per unit time. Recycle ratios willbe discussed further in the following.

Piping is also provided for connecting a pump discharge with itsdownstream wetland cell. In a particular embodiment a check valve can bepositioned in the pipe for permitting flow toward the wetland cell 56,and for preventing return flow. The piping is in fluid communicationwith the distribution pipe 25, which has a plurality of holes forpermitting spreading of the water exiting the upstream lagoon 55 overthe surface of the wetland cell 56.

A unified environmental space 80 (FIG. 6) includes the systems 10,50 ofthe present invention and their associated elements. For example, thesystems 10,50 may be positionable within a solarium-type room 81 thathas windows 82 that are automatically openable in response to inside andoutside temperatures to optimize comfort of the inhabitants andoperation of the systems 10,50.

This unified environmental space 80 may also form a part of a businessmethod, wherein an offer is made to a customer to sell or lease a livingspace including one of the systems 10,50 described above.

The systems 10,50 of the present invention provide advanced, onsitetreatment of wastewater, which has typically been achieved with septictanks and leach fields. Better onsite treatment is desirable to protectgroundwater resources.

The systems 10,50 may be included within or attached to a single home, agroup of residences, or a unit such as a hotel or resort, with thewetland components requiring sunlight that is accessible either out ofdoors or within a sunroom-type enclosure.

The systems 10,50 provide the minimum design treatment standards listedin Table 1.

TABLE 1 Minimum Design Treatment Standards Parameter Effluent StandardNote BOD₅ <15 mg/L <5 mg/L achievable in some embodiments Total nitrogen<15 mg/L <5 mg/L achievable in some embodiments Ammonia  <3 mg/L <0.2mg/L achievable in some embodiments Phosphorus 30% removal 100% ofphosphorus is absorbed in most soils if subsurface effluent dispersal isused TSS <15 mg/L <5 mg/L achievable in some embodiments Fecal coliforms<100 cfu/100 ml If ultraviolet disinfection used

In the foregoing description, certain terms have been used for brevity,clarity, and understanding, but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchwords are used for description purposes herein and are intended to bebroadly construed. Moreover, the embodiments of the apparatusillustrated and described herein are by way of example, and the scope ofthe invention is not limited to the exact details of construction.

Having now described the invention, the construction, the operation anduse of preferred embodiments thereof, and the advantageous new anduseful results obtained thereby, the new and useful constructions, andreasonable mechanical equivalents thereof obvious to those skilled inthe art, are set forth in the appended claims.

1. A method for achieving advanced treatment of wastewater comprising:removing from water to be treated at least some organic compounds andsolids in a first module; at least intermittently exposing the water tobe treated to oxygen in the first module; achieving at least partialdenitrification of the water to be treated in the first module;channeling the water from the first module to a second module comprisingan aerated hydroponic reactor; and channeling water exiting thehydroponic reactor to a top of a third module comprising a vertical-flowwetland adapted to maintain a population of aquatic invertebratestherein, for achieving BOD removal, nitrification, denitrification, andremoval of TSS.
 2. The method recited in claim 1, further comprising thestep of performing an initial partial organic and solids removal on thewater in an anaerobic environment, prior to entry into the first module.3. The method recited in claim 2, further comprising filtering effluentbetween the anaerobic environment and the first module.
 4. The methodrecited in claim 2, further comprising recycling some of the waterexiting the hydroponic reactor to the first module.
 5. The methodrecited in claim 1, further comprising the step of shielding the waterentering the wetland from the atmosphere.
 6. The method recited in claim1, wherein the wetland comprises a mat adapted for permitting plants toroot therein and particulate medium positioned beneath the mat.
 7. Themethod recited in claim 6, wherein the particulate medium comprises alayer of plastic media adapted to support a growth of a biofilm thereonand to permit plant root growth thereinto.
 8. The method recited inclaim 7, wherein the particulate medium further comprises a layer ofmanufactured aggregate penetrable by plant roots, the manufacturedaggregate layer positioned beneath the plastic media layer.
 9. Themethod recited in claim 8, wherein the particulate medium furthercomprises a layer of gravel positioned beneath the manufacturedaggregate layer.
 10. The method recited in claim 9, further comprisingthe step of intermittently draining the gravel layer, for exposing thegravel layer to air.
 11. The method recited in claim 1, furthercomprising the step of disinfecting effluent from the wetland usingultraviolet light.
 12. A method for advanced treatment of wastewatercomprising: removing from water to be treated at least some organiccompounds and solids in a first module; at least intermittently exposingthe water to be treated to oxygen in the first module; achieving atleast partial denitrification of the water to be treated in the firstmodule; channeling water exiting the first module to a lagoon, thelagoon adapted to function essentially aerobically and to contain plantshaving roots positioned to contact water flowing thereinto; transportingwater exiting the lagoon to a vertical flow wetland cell, the wetlandcell adapted to contain plants having roots positioned to contact waterflowing thereinto; recycling at least a portion of the water exiting abottom of the wetland cell to the lagoon; recycling at least a portionof the water exiting the bottom of the wetland to a location upstream ofthe first module.
 13. A method for achieving advanced treatment ofwastewater comprising the steps of: filtering water to be treated withan attached growth pretreatment filter at least intermittently exposedto atmospheric oxygen; transferring water from a filter outlet to aninlet of a hydroponic reactor; distributing water from an outlet of thehydroponic reactor to a vertical-flow wetland comprising a basin havingan outlet in a bottom thereof, the basin adapted to contain aparticulate medium, and a mat adapted for permitting plants to roottherein, the mat positioned above the particulate medium, the wetlandcell adapted to maintain a population of aquatic invertebrates therein.14. The method recited in claim 13, wherein an inlet of the filter isadapted to receive water to be treated from a primary tank.
 15. Themethod recited in claim 14, wherein the primary tank comprises a passiveanaerobic reactor and settling basin.
 16. The method recited in claim13, wherein the reactor comprises a basin having an inlet and an outlet,and a rack positionable at a surface of water in the basin forsupporting plants thereon.
 17. The method recited in claim 13, whereinthe water distributing step comprises positioning a distributionmanifold atop the mat and the wetland further comprises a dressingmaterial positioned atop the distribution manifold.
 18. The methodrecited in claim 13, wherein the particulate medium comprises a layer ofplastic media adapted to support a growth of a biofilm thereon and topermit plant root growth thereinto, the plastic media layer positionedbeneath the mat.
 19. The method recited in claim 13, further comprisingchanneling water exiting the wetland outlet to a drainage sump anddividing the water from the drainage sump among the primary tank, thefilter, and a basin discharge outlet.
 20. The method recited in claim19, further comprising the step of treating water emerging from thebasin discharge outlet with ultraviolet disinfection.